The present invention relates to a scanning mechanism that performs scanning with a light beam such as a laser beam. The present invention also relates to a method of machining various types of workpieces, and to a machine tool.
To machine various types of workpieces, laser machining is typically used. For the laser machining, a laser beam is emitted on a surface of a workpiece by a laser oscillator. Modern laser machining requires that the emitted laser beam be guided by optical elements such as a lens and a mirror, to scan a desired position of the workpiece.
Laser machining currently works as follows.
In the first type, a high power laser oscillator is used and applied to high intensity, high speed welding. For example, the automobile industry uses this type of laser machining.
In the second type, a low power laser oscillator is used and applied to micromachining. For example, a business category such as the electronic industry uses this type of laser machining. When laser machining is applied to micromachining, a laser beam has to be collected into a fine spot with a diameter of 100 μm or smaller so as to irradiate a machining object with the collected light beam for machining.
Examples of micromachining members include a suspension used in a magnetic disk unit, and a head gimbal assembly (HGA) in which a magnetic head slider is mounted at a tip of a suspension. These members visually require adjustment machining for the roll angle, pitch angle, and spring pressure thereof. In a case where a laser formation technique is applied to such adjustment machining, since the members are becoming more miniaturized and hence the angles and spring pressure have to be finely adjusted, the diameter of a laser beam to be emitted on the members is desired to be as fine as about 10 to 30 μm.
In addition, in the above-mentioned adjustment machining, the angles and spring pressure of the members have to be adjusted, in both plus and minus directions. Thus, a laser beam must be collected to scan both front side and rear side of the HGA for the suspension, as a workpiece.
Meanwhile, when laser machining is being performed, the temperature of the member decreases, as thermal energy accumulated in a portion of the member irradiated with the laser beam diffuses around the member. However, as the machining members are becoming more miniaturized, the speed of decrease in temperature by diffusion of the thermal energies reduced. As a result, the portion of the machining member irradiated with the laser beam tends to become overheated. Therefore, it may be difficult to keep providing an efficient forming condition. Thus, a heat gain through the laser scanning is necessary to be reduced and stabilized.
FIG. 1 is an illustration showing an example of an optical scanner of a related art capable of scanning both front and rear sides of a workpiece with a laser beam.
The optical scanner shown in FIG. 1 has laser oscillators for both the front side and the rear side of a workpiece, a plurality of galvano scanners that perform scanning using laser beams emitted by respective laser oscillators, and a plurality of fθ lenses (telocentric lenses) that collect the laser beams for scanning from respective galvano scanners and determine irradiation positions of the laser beams. With the optical scanner shown in FIG. 1, the laser beams can be positioned at high speed.
FIG. 2 is an illustration showing another example of an optical scanner of the related art.
In the scanner shown in FIG. 2, a split unit splits a laser beam emitted by a single laser oscillator into two laser parts. Then, optical fibers guide the first laser part to a front-side irradiation unit that irradiates a front side of a workpiece with the first laser part, and guide the second laser part to a rear-side irradiation unit that irradiates a rear side of the workplace with the second laser part.
The front-side and rear-side irradiation units include optical systems that collect laser beams on surfaces of the workpiece. Also, the irradiation units are connected to an actuator via a supporting member, so as to be driven in a direction indicated by an arrow in the drawing (in a plane). The scanning of the laser beam on the front and rear sides of the workpiece can be performed by driving the irradiation units.
FIG. 3 is an illustration showing still another example of an optical scanner of the related art. FIG. 3 is a modification of the optical scanner shown in FIG. 2. While the workpiece is fixed in the optical scanner shown in FIG. 2, irradiation units are fixed and a workpiece is connected to an actuator in the optical scanner as shown in FIG. 3.
The workpiece is shifted in a plane indicated by an arrow in the drawing by driving the actuator. Accordingly, laser beams emitted by the irradiation units can scan surfaces of the workpiece (See Japanese Unexamined Patent Application Publication No. 5-164987)
The optical scanner shown in FIG. 1 can perform positioning at high speed as described above. However, the galvano scanner serving as a scanning mechanism is expensive, and hence, the entire price of the optical scanner becomes expensive.
In contrast, the optical scanner shown in FIG. 2 or 3 employs a relatively simple mechanism for guiding the laser beam, thereby reducing the cost. However, since the optical fiber is used, it is difficult to decrease the spot diameter of the laser beam to be equal to or smaller than the core diameter of the optical fiber. Hence, the optical fiber cannot be used for fine machining.
In particular, the optical scanner that is shown in FIG. 3 shifts the workpiece. If the workpiece is large and heavy, a drive source such as a large actuator is required for positioning of the scanning position. Further, positioning at high speed or with high accuracy is relatively difficult.
An object of the present invention is to provide a scanning mechanism that can overcome the above problems. Also, another object of the present invention is to provide a method of machining a workpiece and to provide a machine tool that can overcome the above problems.